Neonates are incapable of maintaining their own body temperature during the first few weeks of life. Skin perfusion rates are very high and the infant loses heat rapidly. Thermal management is critical, requiring an accurate, fast, noninvasive method of core temperature measurement.
Rectal temperature has long been considered to be the standard indicator of neonate core temperature. However, since temperature measurements from different locations on a neonate's skin are sufficiently uniform as to be relatively interchangeable with one another, the clinician may select the most noninvasive and convenient site at which to measure temperature. Due to its inherent safety and long established efficacy, axilla (underarm) is the most recommended site for neonates. Unfortunately, conventional thermometers such as glass/mercury, electronic and paper strip thermometers require up to several minutes to obtain an accurate axillary reading.
In recent years, infrared thermometers have come into wide use for detection of temperature of adults. For core temperature readings, infrared thermometers which are adapted to be inserted into the patient's ear have been extremely successful.
Infrared ear thermometry has not found such high acceptance for use with neonates. Neonates have a very high moisture level in their ear canals, due to the presence of vernix and residual amniotic fluid, resulting in low tympanic temperatures because of the associative evaporative cooling. In addition, environmental uncertainties, such as radiant heaters and warming pads can significantly influence the air temperature. Further, clinicians are less inclined to position the tip of an infrared thermometer in the ear of a small neonate.
An infrared thermometer designed for axillary temperature measurements is presented in U.S. patent application Ser. No. 08/469,484. In that device, an infrared detector probe extends from a temperature display housing and may easily slide into the axilla to lightly touch the apex of the axilla and provide an accurate infrared temperature reading in as little as one-half second.
The axillary infrared thermometer has found great utility not only with neonates but as a screening tool in general and especially for small children where conventional temperature measurements such as a thermometer under the tongue or a rectal thermometer are difficult. The axillary measurement is particularly accurate with children where there is a lack of axillary hair and perspiration.